The scarcity and cost of oil and gas for use in home heating plants has drastically affected the continued use of such fuel. The availability of coal as a fuel compels its consideration as a source for domestic heating purposes, particularly if the inherent disadvantages of its use such as the difficulty in storage and handling, the polluting products of coal combustion, and the disposal of solid waste products of combustion can be overcome or minimized.
The conventional hopper-fed automatically stoked home furnace, with air to support combustion at or below the coal bed, is subject to all of the major disadvantages mentioned. Loose coal must be stored and loaded into the hopper with the attendant handling problems and dust. Combustion of coal in a typical domestic furnace is characterized by changing conditions in the fuel bed. The stoker feeds coal by auger and is cycled on and off by a thermostat control. When the stoker is on, coal is fed at a constant rate into a furnace retort that is supplied with air by a blower. Temperature in the fuel bed rises gradually, increasing the rate of heat release. The temperature of the fuel bed generally does not reach a steady state before the thermostat stops the fuel feed and blower. Upon shut-down of the latter elements, the fuel bed continues to burn at a slow rate which is limited by the natural draft air supply of the furnace. Because the combustion reaction is limited by air supply, combustion is not complete during this cool down period leading to the formation of hydrocarbons, carbon monoxide and soot in the exhaust. Since ash is dropped through the grate and from the sides of the bed into relatively cool regions, periodic cool down is necessary to prevent the ash from agglomerating into chunks too large to be removed. As a result, even when an underfeed stoker is operated at full load, ash disposal makes it necessary to shut down periodically to allow the ash to cool and fuse to avoid the formation of large clinkers. To maintain ignition in no load operation, the fuel bed must be fired briefly at intervals.
It is desirable, therefore, to provide a solid fuel burning arrangement in which the fuel is made available in a consolidated prepared form to eliminate the difficulty and dirt associated with the handling of loose coal. Since much of the pollutant formation in domesitc stoker furnaces is the result of transient phenomena in the fuel bed, it is desirable to provide a burner which burns the fuel in a steady manner to permit more complete combustion and improve the quality of furnace emissions. Fuel additives tailored to improve performance and reduce pollutants are also desirable. Combustion arrangements that provide continuous ash removal thus eliminating periodic cooldowns, and which allow all of the fuel to be burned would also improve emissions. These and additional desirable features are achieved by the fuel cartridge and burner disclosed herein.